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526 lines
14 KiB
526 lines
14 KiB
// SPDX-License-Identifier: GPL-2.0-only |
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/* |
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* Bitbanging I2C bus driver using the GPIO API |
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* |
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* Copyright (C) 2007 Atmel Corporation |
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*/ |
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#include <linux/completion.h> |
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#include <linux/debugfs.h> |
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#include <linux/delay.h> |
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#include <linux/gpio/consumer.h> |
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#include <linux/i2c-algo-bit.h> |
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#include <linux/i2c.h> |
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#include <linux/init.h> |
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#include <linux/interrupt.h> |
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#include <linux/module.h> |
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#include <linux/of.h> |
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#include <linux/platform_data/i2c-gpio.h> |
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#include <linux/platform_device.h> |
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#include <linux/slab.h> |
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struct i2c_gpio_private_data { |
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struct gpio_desc *sda; |
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struct gpio_desc *scl; |
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struct i2c_adapter adap; |
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struct i2c_algo_bit_data bit_data; |
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struct i2c_gpio_platform_data pdata; |
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#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR |
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struct dentry *debug_dir; |
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/* these must be protected by bus lock */ |
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struct completion scl_irq_completion; |
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u64 scl_irq_data; |
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#endif |
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}; |
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/* |
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* Toggle SDA by changing the output value of the pin. This is only |
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* valid for pins configured as open drain (i.e. setting the value |
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* high effectively turns off the output driver.) |
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*/ |
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static void i2c_gpio_setsda_val(void *data, int state) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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gpiod_set_value_cansleep(priv->sda, state); |
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} |
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/* |
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* Toggle SCL by changing the output value of the pin. This is used |
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* for pins that are configured as open drain and for output-only |
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* pins. The latter case will break the i2c protocol, but it will |
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* often work in practice. |
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*/ |
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static void i2c_gpio_setscl_val(void *data, int state) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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gpiod_set_value_cansleep(priv->scl, state); |
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} |
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static int i2c_gpio_getsda(void *data) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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return gpiod_get_value_cansleep(priv->sda); |
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} |
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static int i2c_gpio_getscl(void *data) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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return gpiod_get_value_cansleep(priv->scl); |
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} |
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#ifdef CONFIG_I2C_GPIO_FAULT_INJECTOR |
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static struct dentry *i2c_gpio_debug_dir; |
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#define setsda(bd, val) ((bd)->setsda((bd)->data, val)) |
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#define setscl(bd, val) ((bd)->setscl((bd)->data, val)) |
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#define getsda(bd) ((bd)->getsda((bd)->data)) |
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#define getscl(bd) ((bd)->getscl((bd)->data)) |
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#define WIRE_ATTRIBUTE(wire) \ |
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static int fops_##wire##_get(void *data, u64 *val) \ |
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{ \ |
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struct i2c_gpio_private_data *priv = data; \ |
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\ |
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i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
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*val = get##wire(&priv->bit_data); \ |
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i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
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return 0; \ |
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} \ |
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static int fops_##wire##_set(void *data, u64 val) \ |
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{ \ |
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struct i2c_gpio_private_data *priv = data; \ |
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\ |
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i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
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set##wire(&priv->bit_data, val); \ |
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i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); \ |
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return 0; \ |
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} \ |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_##wire, fops_##wire##_get, fops_##wire##_set, "%llu\n") |
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WIRE_ATTRIBUTE(scl); |
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WIRE_ATTRIBUTE(sda); |
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static void i2c_gpio_incomplete_transfer(struct i2c_gpio_private_data *priv, |
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u32 pattern, u8 pattern_size) |
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{ |
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struct i2c_algo_bit_data *bit_data = &priv->bit_data; |
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int i; |
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i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); |
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/* START condition */ |
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setsda(bit_data, 0); |
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udelay(bit_data->udelay); |
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/* Send pattern, request ACK, don't send STOP */ |
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for (i = pattern_size - 1; i >= 0; i--) { |
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setscl(bit_data, 0); |
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udelay(bit_data->udelay / 2); |
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setsda(bit_data, (pattern >> i) & 1); |
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udelay((bit_data->udelay + 1) / 2); |
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setscl(bit_data, 1); |
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udelay(bit_data->udelay); |
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} |
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i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); |
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} |
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static int fops_incomplete_addr_phase_set(void *data, u64 addr) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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u32 pattern; |
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if (addr > 0x7f) |
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return -EINVAL; |
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/* ADDR (7 bit) + RD (1 bit) + Client ACK, keep SDA hi (1 bit) */ |
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pattern = (addr << 2) | 3; |
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i2c_gpio_incomplete_transfer(priv, pattern, 9); |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_addr_phase, NULL, fops_incomplete_addr_phase_set, "%llu\n"); |
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static int fops_incomplete_write_byte_set(void *data, u64 addr) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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u32 pattern; |
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if (addr > 0x7f) |
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return -EINVAL; |
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/* ADDR (7 bit) + WR (1 bit) + Client ACK (1 bit) */ |
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pattern = (addr << 2) | 1; |
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/* 0x00 (8 bit) + Client ACK, keep SDA hi (1 bit) */ |
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pattern = (pattern << 9) | 1; |
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i2c_gpio_incomplete_transfer(priv, pattern, 18); |
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return 0; |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_incomplete_write_byte, NULL, fops_incomplete_write_byte_set, "%llu\n"); |
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static int i2c_gpio_fi_act_on_scl_irq(struct i2c_gpio_private_data *priv, |
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irqreturn_t handler(int, void*)) |
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{ |
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int ret, irq = gpiod_to_irq(priv->scl); |
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if (irq < 0) |
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return irq; |
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i2c_lock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); |
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ret = gpiod_direction_input(priv->scl); |
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if (ret) |
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goto unlock; |
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reinit_completion(&priv->scl_irq_completion); |
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ret = request_irq(irq, handler, IRQF_TRIGGER_FALLING, |
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"i2c_gpio_fault_injector_scl_irq", priv); |
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if (ret) |
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goto output; |
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wait_for_completion_interruptible(&priv->scl_irq_completion); |
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free_irq(irq, priv); |
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output: |
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ret = gpiod_direction_output(priv->scl, 1) ?: ret; |
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unlock: |
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i2c_unlock_bus(&priv->adap, I2C_LOCK_ROOT_ADAPTER); |
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return ret; |
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} |
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static irqreturn_t lose_arbitration_irq(int irq, void *dev_id) |
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{ |
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struct i2c_gpio_private_data *priv = dev_id; |
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setsda(&priv->bit_data, 0); |
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udelay(priv->scl_irq_data); |
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setsda(&priv->bit_data, 1); |
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complete(&priv->scl_irq_completion); |
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return IRQ_HANDLED; |
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} |
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static int fops_lose_arbitration_set(void *data, u64 duration) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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if (duration > 100 * 1000) |
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return -EINVAL; |
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priv->scl_irq_data = duration; |
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/* |
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* Interrupt on falling SCL. This ensures that the master under test has |
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* really started the transfer. Interrupt on falling SDA did only |
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* exercise 'bus busy' detection on some HW but not 'arbitration lost'. |
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* Note that the interrupt latency may cause the first bits to be |
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* transmitted correctly. |
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*/ |
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return i2c_gpio_fi_act_on_scl_irq(priv, lose_arbitration_irq); |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_lose_arbitration, NULL, fops_lose_arbitration_set, "%llu\n"); |
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static irqreturn_t inject_panic_irq(int irq, void *dev_id) |
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{ |
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struct i2c_gpio_private_data *priv = dev_id; |
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udelay(priv->scl_irq_data); |
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panic("I2C fault injector induced panic"); |
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return IRQ_HANDLED; |
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} |
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static int fops_inject_panic_set(void *data, u64 duration) |
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{ |
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struct i2c_gpio_private_data *priv = data; |
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if (duration > 100 * 1000) |
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return -EINVAL; |
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priv->scl_irq_data = duration; |
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/* |
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* Interrupt on falling SCL. This ensures that the master under test has |
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* really started the transfer. |
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*/ |
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return i2c_gpio_fi_act_on_scl_irq(priv, inject_panic_irq); |
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} |
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DEFINE_DEBUGFS_ATTRIBUTE(fops_inject_panic, NULL, fops_inject_panic_set, "%llu\n"); |
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static void i2c_gpio_fault_injector_init(struct platform_device *pdev) |
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{ |
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struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev); |
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/* |
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* If there will be a debugfs-dir per i2c adapter somewhen, put the |
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* 'fault-injector' dir there. Until then, we have a global dir with |
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* all adapters as subdirs. |
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*/ |
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if (!i2c_gpio_debug_dir) { |
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i2c_gpio_debug_dir = debugfs_create_dir("i2c-fault-injector", NULL); |
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if (!i2c_gpio_debug_dir) |
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return; |
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} |
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priv->debug_dir = debugfs_create_dir(pdev->name, i2c_gpio_debug_dir); |
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if (!priv->debug_dir) |
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return; |
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init_completion(&priv->scl_irq_completion); |
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debugfs_create_file_unsafe("incomplete_address_phase", 0200, priv->debug_dir, |
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priv, &fops_incomplete_addr_phase); |
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debugfs_create_file_unsafe("incomplete_write_byte", 0200, priv->debug_dir, |
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priv, &fops_incomplete_write_byte); |
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if (priv->bit_data.getscl) { |
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debugfs_create_file_unsafe("inject_panic", 0200, priv->debug_dir, |
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priv, &fops_inject_panic); |
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debugfs_create_file_unsafe("lose_arbitration", 0200, priv->debug_dir, |
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priv, &fops_lose_arbitration); |
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} |
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debugfs_create_file_unsafe("scl", 0600, priv->debug_dir, priv, &fops_scl); |
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debugfs_create_file_unsafe("sda", 0600, priv->debug_dir, priv, &fops_sda); |
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} |
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static void i2c_gpio_fault_injector_exit(struct platform_device *pdev) |
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{ |
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struct i2c_gpio_private_data *priv = platform_get_drvdata(pdev); |
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debugfs_remove_recursive(priv->debug_dir); |
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} |
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#else |
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static inline void i2c_gpio_fault_injector_init(struct platform_device *pdev) {} |
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static inline void i2c_gpio_fault_injector_exit(struct platform_device *pdev) {} |
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#endif /* CONFIG_I2C_GPIO_FAULT_INJECTOR*/ |
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static void of_i2c_gpio_get_props(struct device_node *np, |
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struct i2c_gpio_platform_data *pdata) |
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{ |
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u32 reg; |
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of_property_read_u32(np, "i2c-gpio,delay-us", &pdata->udelay); |
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if (!of_property_read_u32(np, "i2c-gpio,timeout-ms", ®)) |
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pdata->timeout = msecs_to_jiffies(reg); |
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pdata->sda_is_open_drain = |
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of_property_read_bool(np, "i2c-gpio,sda-open-drain"); |
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pdata->scl_is_open_drain = |
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of_property_read_bool(np, "i2c-gpio,scl-open-drain"); |
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pdata->scl_is_output_only = |
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of_property_read_bool(np, "i2c-gpio,scl-output-only"); |
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} |
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static struct gpio_desc *i2c_gpio_get_desc(struct device *dev, |
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const char *con_id, |
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unsigned int index, |
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enum gpiod_flags gflags) |
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{ |
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struct gpio_desc *retdesc; |
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int ret; |
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retdesc = devm_gpiod_get(dev, con_id, gflags); |
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if (!IS_ERR(retdesc)) { |
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dev_dbg(dev, "got GPIO from name %s\n", con_id); |
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return retdesc; |
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} |
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retdesc = devm_gpiod_get_index(dev, NULL, index, gflags); |
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if (!IS_ERR(retdesc)) { |
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dev_dbg(dev, "got GPIO from index %u\n", index); |
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return retdesc; |
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} |
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ret = PTR_ERR(retdesc); |
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/* FIXME: hack in the old code, is this really necessary? */ |
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if (ret == -EINVAL) |
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retdesc = ERR_PTR(-EPROBE_DEFER); |
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/* This happens if the GPIO driver is not yet probed, let's defer */ |
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if (ret == -ENOENT) |
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retdesc = ERR_PTR(-EPROBE_DEFER); |
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if (PTR_ERR(retdesc) != -EPROBE_DEFER) |
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dev_err(dev, "error trying to get descriptor: %d\n", ret); |
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return retdesc; |
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} |
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static int i2c_gpio_probe(struct platform_device *pdev) |
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{ |
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struct i2c_gpio_private_data *priv; |
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struct i2c_gpio_platform_data *pdata; |
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struct i2c_algo_bit_data *bit_data; |
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struct i2c_adapter *adap; |
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struct device *dev = &pdev->dev; |
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struct device_node *np = dev->of_node; |
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enum gpiod_flags gflags; |
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int ret; |
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priv = devm_kzalloc(dev, sizeof(*priv), GFP_KERNEL); |
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if (!priv) |
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return -ENOMEM; |
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adap = &priv->adap; |
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bit_data = &priv->bit_data; |
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pdata = &priv->pdata; |
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if (np) { |
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of_i2c_gpio_get_props(np, pdata); |
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} else { |
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/* |
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* If all platform data settings are zero it is OK |
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* to not provide any platform data from the board. |
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*/ |
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if (dev_get_platdata(dev)) |
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memcpy(pdata, dev_get_platdata(dev), sizeof(*pdata)); |
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} |
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/* |
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* First get the GPIO pins; if it fails, we'll defer the probe. |
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* If the SCL/SDA lines are marked "open drain" by platform data or |
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* device tree then this means that something outside of our control is |
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* marking these lines to be handled as open drain, and we should just |
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* handle them as we handle any other output. Else we enforce open |
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* drain as this is required for an I2C bus. |
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*/ |
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if (pdata->sda_is_open_drain) |
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gflags = GPIOD_OUT_HIGH; |
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else |
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gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; |
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priv->sda = i2c_gpio_get_desc(dev, "sda", 0, gflags); |
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if (IS_ERR(priv->sda)) |
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return PTR_ERR(priv->sda); |
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if (pdata->scl_is_open_drain) |
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gflags = GPIOD_OUT_HIGH; |
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else |
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gflags = GPIOD_OUT_HIGH_OPEN_DRAIN; |
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priv->scl = i2c_gpio_get_desc(dev, "scl", 1, gflags); |
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if (IS_ERR(priv->scl)) |
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return PTR_ERR(priv->scl); |
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if (gpiod_cansleep(priv->sda) || gpiod_cansleep(priv->scl)) |
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dev_warn(dev, "Slow GPIO pins might wreak havoc into I2C/SMBus bus timing"); |
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else |
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bit_data->can_do_atomic = true; |
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bit_data->setsda = i2c_gpio_setsda_val; |
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bit_data->setscl = i2c_gpio_setscl_val; |
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if (!pdata->scl_is_output_only) |
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bit_data->getscl = i2c_gpio_getscl; |
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bit_data->getsda = i2c_gpio_getsda; |
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if (pdata->udelay) |
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bit_data->udelay = pdata->udelay; |
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else if (pdata->scl_is_output_only) |
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bit_data->udelay = 50; /* 10 kHz */ |
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else |
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bit_data->udelay = 5; /* 100 kHz */ |
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if (pdata->timeout) |
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bit_data->timeout = pdata->timeout; |
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else |
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bit_data->timeout = HZ / 10; /* 100 ms */ |
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bit_data->data = priv; |
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adap->owner = THIS_MODULE; |
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if (np) |
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strlcpy(adap->name, dev_name(dev), sizeof(adap->name)); |
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else |
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snprintf(adap->name, sizeof(adap->name), "i2c-gpio%d", pdev->id); |
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adap->algo_data = bit_data; |
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adap->class = I2C_CLASS_HWMON | I2C_CLASS_SPD; |
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adap->dev.parent = dev; |
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adap->dev.of_node = np; |
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if (pdev->id != PLATFORM_DEVID_NONE || !pdev->dev.of_node || |
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of_property_read_u32(pdev->dev.of_node, "reg", &adap->nr)) |
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adap->nr = pdev->id; |
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ret = i2c_bit_add_numbered_bus(adap); |
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if (ret) |
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return ret; |
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platform_set_drvdata(pdev, priv); |
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/* |
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* FIXME: using global GPIO numbers is not helpful. If/when we |
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* get accessors to get the actual name of the GPIO line, |
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* from the descriptor, then provide that instead. |
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*/ |
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dev_info(dev, "using lines %u (SDA) and %u (SCL%s)\n", |
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desc_to_gpio(priv->sda), desc_to_gpio(priv->scl), |
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pdata->scl_is_output_only |
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? ", no clock stretching" : ""); |
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i2c_gpio_fault_injector_init(pdev); |
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return 0; |
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} |
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static int i2c_gpio_remove(struct platform_device *pdev) |
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{ |
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struct i2c_gpio_private_data *priv; |
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struct i2c_adapter *adap; |
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i2c_gpio_fault_injector_exit(pdev); |
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priv = platform_get_drvdata(pdev); |
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adap = &priv->adap; |
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i2c_del_adapter(adap); |
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return 0; |
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} |
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#if defined(CONFIG_OF) |
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static const struct of_device_id i2c_gpio_dt_ids[] = { |
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{ .compatible = "i2c-gpio", }, |
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{ /* sentinel */ } |
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}; |
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MODULE_DEVICE_TABLE(of, i2c_gpio_dt_ids); |
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#endif |
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static struct platform_driver i2c_gpio_driver = { |
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.driver = { |
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.name = "i2c-gpio", |
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.of_match_table = of_match_ptr(i2c_gpio_dt_ids), |
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}, |
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.probe = i2c_gpio_probe, |
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.remove = i2c_gpio_remove, |
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}; |
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static int __init i2c_gpio_init(void) |
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{ |
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int ret; |
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ret = platform_driver_register(&i2c_gpio_driver); |
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if (ret) |
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printk(KERN_ERR "i2c-gpio: probe failed: %d\n", ret); |
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return ret; |
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} |
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subsys_initcall(i2c_gpio_init); |
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static void __exit i2c_gpio_exit(void) |
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{ |
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platform_driver_unregister(&i2c_gpio_driver); |
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} |
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module_exit(i2c_gpio_exit); |
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MODULE_AUTHOR("Haavard Skinnemoen (Atmel)"); |
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MODULE_DESCRIPTION("Platform-independent bitbanging I2C driver"); |
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MODULE_LICENSE("GPL v2"); |
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MODULE_ALIAS("platform:i2c-gpio");
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